Systems that locate gunshots based on time of arrival of the gunshot sound at a number of microphones relay the sound to a central controller using open analog lines, for example telephone lines. The central controller can then locate the source of the gunshot sound relative to the microphone locations using the relative arrival times at the various microphones. The microphones are typically located on telephone poles, and these systems can locate a gunshot to a region the size of a city block. Greater accuracy can be obtained by using more microphone, computing and communication line resources. However these systems do not scale well as they require open analog lines having well characterized delays in order to accurately determine the location of an acoustic source.
In other acoustic location systems, acoustic signals are sampled and stored at a number of microphones. Samples within a given time range are requested by a central controller in order to calculate the acoustic source location using time of arrival information from each of the requested microphones. The time ranges requested for each microphone are offset according to their location and the relative timing differences between their respective local clocks. This system however is processor and memory intensive.
In yet other acoustic location systems, by knowing in advance the times at which acoustic signals will be emitted, acoustic sensors can determine their respective ranges to the source of the acoustic signal (knowing the speed of sound) and then use triangulation to determine the position of the acoustic source.
Enhancement of acoustic signals received from an acoustic source having a determined location can be achieved using directional microphones. Other solutions attempt to remove noise from the received signal.